In a long-term evolution-advanced (LTE-A) carrier aggregation (CA) system, multiple carriers are aggregated, and may communicate with a single piece of user equipment (UE, which may also be referred to as a terminal or terminal equipment) at the same time. That is, one piece of UE has multiple serving cells. In the multiple serving cells, one is a primary cell (PCell), and others are secondary cells (SCells).
Meanwhile, in multiple processes of the LTE-A CA system, there are different MAC CEs which control the UE or are used for transmission various information, such as a discontinuous reception (DRX) control process, an uplink time adjustment process, a power headroom report and a buffer status report (BSR), etc. Such processes are necessary for normal operation of the LTE-A CA system, and the MAC CEs are signaling indispensable to control of these processes. Therefore, in a process of logic channel prioritization (LCP) in the LTE-A CA system, priorities of different MAC CEs and data of different logic channel are (in a descending order):
cell radio network temporary identifier (C-RNTI) MAC CEs or data transmitted on uplink common control channels (UL-CCCHs);
MAC CEs for BSR with exception of BSR included for padding;
MAC CEs for a power headroom report (PHR) or an extended PHR;
data transmitted on any logic channels with exception of UL-CCCHs; and
MAC CEs for BSR included for padding.
It can be seen from the above order of priorities that UE data (data included in “data transmitted on any logic channels with exception of UL-CCCHs”) have secondarily lowest priorities, while priorities of most of the MAC CEs (with exception of MAC CEs for BSR included for padding) are higher than those of the UE data.
Hence, in a current LTE-A system, when UE receives uplink grants allocated for one or more cells in a transmission time interval (TTI), as these cells are all in a licensed band, the UE will deem that channel quality of these cells is similar, not differentiate these cells, and select appropriate cells for different MAC CEs or data after selecting the MAC CEs or data according to the principle of descending order of priorities, and transmit the MAC CEs or data on the selected cells.
In selecting cells for different MAC CEs or data, the UE may obey a manner of implementation of itself, and no principle or method for selecting cells is provided in the current protocols.
It should be noted that the above description of the background is merely provided for clear and complete explanation of this disclosure and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background of this disclosure.